This contract will provide NLM with research support for the maintenance and enhancement of the UMLS Metathesaurus. Work will focus on six areas: (1) analysis of the structure and semantics of a variety of biomedical vocabularies and databases; (2) the development of the logic and algorithms for preprocessing and editing these sources so data from them can be merged by the Metathesaurus maintenance engine; (3) development of algorithms for the simultaneous maintenance of multiple source vocabularies within the Metathesaurus environment; (4) the lexical and semantic analysis of the Metathesaurus to identify potential errors and omitted relationships; (5) definition of the structure and capabilities required to support high performance remote editing and distributed maintenance of the Metathesaurus; and (6) the development of procedures for more effective electronic dissemination of the Metathesaurus.